Light emitting diodes (LEDs) will play an increasingly significant role in general lighting in the future. This will result in more and more new installations being equipped with LED light sources in various ways. The reason for replacing state of the art light sources with LED light sources is the low power consumption of LED light sources and their extremely long lifetime.
Further, compared to the lifetime of for example fluorescent type light sources, the lifetime of respective housings for receiving the fluorescent type light sources and the respective drivers for powering the fluorescent type light sources is rather long. Thus, it seems to be attractive if a user could simply replace such kind of fluorescent type light sources.
However, there is the problem that modern electronic ballasts or drivers have identification capabilities of fluorescent light sources like “TL-tubes”, i.e. they measure for example the filaments resistance in order to detect the type of TL-tube connected to the ballast. Such a measurement of a filament resistance is advantageous since typically different tube types require different driving power requirements. For example, the length of a TL-tube influences the burning voltage of the tube and hence the power level. In case an LED retrofit tube is connected to such an intelligent tube driver, due to the presence of LEDs and not simple TL-tube filaments the tube driver might detect a strange filament resistance and hence quit operation.
U.S. Pat. No. 6,936,968 discloses an LED light tube for replacement of fluorescent light tubes including an elongated cylindrical transparent envelope, a base cap at each end of the envelope and at least one LED device in electrical communication with the base cap. The LED light tube is adapted for use in so called troffer-type light fixtures.